Constant practice... find a teacher or a tutor to get feedback from regularly, and hand questions up. This means you will know where your going wrong. Set a plan out for yourself - goals as to when you'll have certain units done. Try your best to meet these goals, and keep on top of it. This'll keep you motivated. Small amounts, and hour or two a week consistantly, and you'll keep on top of it! whatever you do, don't "leave it til last minute" or procrastinate. good luck!
I did the extra subject grinds in DSOG for 5 th year, there are lots of farm trips you have to go on and a project that's worth 25% so I'd definitely recommend doing the grinds in 5 th year now I just do pure revision for 6 th year and studying it on my own